Researchers warn against abrupt stop to geoengineering method

Feb 17, 2014

As a range of climate change mitigation scenarios are discussed, University of Washington researchers have found that the injection of sulfate particles into the atmosphere to reflect sunlight and curb the effects of global warming could pose a severe threat if not maintained indefinitely and supported by strict reductions in greenhouse gas (GHG) emissions.

The new study, published today in Environmental Research Letters, has highlighted the risks of large and spatially expansive temperature increases if solar radiation management (SRM) is abruptly stopped once it has been implemented.

SRM is a proposed method of geoengineering whereby tiny sulfate-based aerosols are released into the upper atmosphere to reflect sunlight and cool the planet. The technique has been shown to be economically and technically feasible; however, its efficacy depends on its continued maintenance, without interruption from technical faults, global cooperation breakdown or funding running dry.

According to the study, global temperature increases could more than double if SRM is implemented for a multi-decadal period of time and then suddenly stopped, in relation to the temperature increases expected if SRM was not implemented at all.

The researchers used a global climate model to show that if an extreme emissions pathway—RCP8.5—is followed up until 2035, allowing temperatures to rise 1°C above the 1970–1999 mean, and then SRM is implemented for 25 years and suddenly stopped, global temperatures could increase by 4°C in the following decades.

This rate of increase, caused by the build-up of background greenhouse gas emissions, would be well beyond the bounds experienced in the last century and more than double the 2°C temperature increase that would occur in the same timeframe if SRM had not been implemented.

On a regional and seasonal scale, the temperature changes would be largest in an absolute sense in winter over high latitude land, but compared to historical fluctuations, temperature changes would be largest in the tropics in summertime, where there is usually very little variation.

Lead author of the research, Kelly McCusker, from the University of Washington, said: "According to our simulations, tropical regions like South Asia and Sub-Saharan Africa are hit particularly hard, the very same regions that are home to many of the world's most food insecure populations. The potential temperature changes also pose a severe threat to biodiversity."

Furthermore, the researchers used a simple climate model to study a variety of plausible greenhouse gas scenarios and SRM termination years over the 21st century. They showed that climate sensitivity—a measure of how much the climate will warm in response to the greenhouse effect—had a lesser impact on the rate of temperature changes.

Instead, they found that the rates of temperature change were determined by the amount of GHG emissions and the duration of time that SRM is deployed.

"The primary control over the magnitude of the large temperature increases after an SRM shutoff is the background greenhouse gas concentrations. Thus, the greater the future emissions of greenhouse gases, the larger the temperature increases would be, and, similarly, the later the termination occurs while GHG emissions continue, the larger the temperature increases," continued McCusker.

"The only way to avoid creating the risk of substantial temperature increases through SRM, therefore, is concurrent strong reductions of GHG emissions."

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User comments : 23

"Humans suffer much more during extreme winters than hot summers. . . . Of particularl concern are the warnings from solar scientists that over the next three decades, we are headed toward significant global cooling as the sun weakens into a grand minimum. The last time the sun was as weak as solar experts predict will occur starting after 2030, the Earth was in a particularly cold phase of the Little Ice Age that lasted from about 1350-1850, a period when there was great misery around the world."

SO much is spent on the myth of global warming. The temperature readings that began in the fifties are used because at that time we were in a geological cooling trend. I remember Lake Erie freezing every year during the middle and late 50s and into the sixties. It will begin again. Used to desperately blame global warming. The desperate cry of jobs, progress and growth killing the planet are political drivel? The polar ice caps are expanding and a cool climate Is once again emerging. I'm sure the liberals will say it s due to progress and growth again and more is needed to quash employment, jobs, growth and expansion.

Another masterpiece from captain obvious. So if we mitigate [the playing hide-and-seek global warming], and then stop mitigating, then the effect of global warming would be more pronounced?Likewise, if I jump from the plane, then decide to mitigate the effect of cruel landing with parachute, and, finally, at the last minute, 100 meters or so, decide to ditch parachute, my landing would be sharp? Give taxpayer grant money back!

From the tone of this article It seems to presume that someone out there is seriously thinking of deliberately attempting to play with the global temperature dynamics by deliberately intoroducing controlled pollution into the atmosphere.

I had presumed that anybody with the audacity to actually consider doing this had already been curbed by the sane masses.

I hope the tone of this article is a complete fabrication and there is no one seriously considering to sulphate our precious atmosphere.

It's curious to watch how far humans will take this idea of treating the models like they are real. Traditionally, what has happened when the models do not work is that somebody applies for more money to fix it. Geoenginering would be a very different sort of endeavor than sitting at a computer, programming models. In the real world, there would be no room for error. So, how does one take these models with a questionable track record, and start up this geoengineering conversation?

I think what's really going on here is that the people who are advocating this stuff need to be immersing themselves in philosophy of science.

I'm confused as to why not upkeeping it will double the warming as this article states?

Is there a particular concentration of sulphates whereby it traps heat? I can't think chemically why putting sulphates into the atmosphere and then stopping this means twice as much energy from the sun is trapped?

I can understand the rate of warming (of which there is currently none) being the same prior to sulphate engineering, but twice as much?

Seems like yet another BS climate change figure.

Also, I hope this doesn't happen, putting sulphates into the atmosphere will have adverse effects as well as the effects wanted.

I'm confused as to why not upkeeping it will double the warming as this article states?

Is there a particular concentration of sulphates whereby it traps heat? I can't think chemically why putting sulphates into the atmosphere and then stopping this means twice as much energy from the sun is trapped?

I can understand the rate of warming (of which there is currently none) being the same prior to sulphate engineering, but twice as much?

Seems like yet another BS climate change figure.

Also, I hope this doesn't happen, putting sulphates into the atmosphere will have adverse effects as well as the effects wanted.

triple: Again the denialist (inconvenient truth) of overlooking the total heat stored by the climate system - the Oceans, that in fact, hold >90% of it.And I assume what is meant by this article is that whilst we can stop warming via aerosol injection. If we stop, due the fact that GHG's have still been building - warming will come back with much stronger feedbacks.

triple: Again the denialist (inconvenient truth) of overlooking the total heat stored by the climate system - the Oceans, that in fact, hold >90% of it.And I assume what is meant by this article is that whilst we can stop warming via aerosol injection. If we stop, due the fact that GHG's have still been building - warming will come back with much stronger feedbacks.

Again, I still don't understand.

1. You have total energy in system, oceans atmosphere, whatever2. You have a rate of energy coming into the planet, and exiting the planet.3. You have a technology that slows the rate of incoming energy by reflecting it.

I don't see how stopping step 3 suddenly means the rate increases by 2x the original rate. Please explain chemically how the rate doubles when the variables in place are identical to prior sulphate processes.

For all intents and purposes how does a continued lowering concentration of sulphates make the oceans or atmosphere absorb twice as much energy?

I cannot see how current level sulphates = X, but current level sulphates after an brief increase = 2X,

You have a heater and a bath of 500ml water, and measure the rate of heatingYou cool it back down, and add 100ml water (our sulphate buffer analogue) and the rate slows down due to more water, and takes longer to warm up.You go back to 500ml, the rate doubles....Erm...

Not to mention that the whole premise of the article is a fairy tale. Are they implying that there is on-off switch to the whole aerosol geoengineering method? That people can't devise a continuous "thermostat-like" regulation? "Oh, temp went up 2 degrees, let's mitigate it a little." "Err, it is freezing out there, shut this thing off". I could imagine some bureaucratic institution at the UN would be quite happy to cease the control over such regulator.

The world has reached ~400 ppm of CO2. We inject aerosols into the Strat and it causes an increase of albedo so that the absorbed Solar SW is reduced such that it gives the equivalent of 280 ppm of GHG warming. We do this for 30 years and all is well with ave global temps. Meanwhile CO2 has been increasing and is up to (say) 450 ppm. You then switch off the aerosol injection - the full solar output is allowed back in and suddenly you have the extra 50 ppm CO2 at work instantly and not a gradual increase that would allow absorption by the oceans. So bang it is manifested quickly in the atmosphere and massive feed-backs would occur - chiefly of Arctic melt altering Earth albedo.

...You then switch off the aerosol injection - the full solar output is allowed back in and suddenly you have the extra 50 ppm CO2 at work instantly and not a gradual increase that would allow absorption by the oceans...

This is possible, but it is just one scenario, and, honestly, not the most probable one.1. You switch off aerosol injection, why?2. "...extra 50 ppm CO2 at work instantly..." - come on, 50 ppm [@400 level] is just 12%. That is far cry from doubling concentration, which would allegedly increase global temp by 2 degrees.3. You pretend to know what heat balance between land and ocean is, but in reality, you have not a slightest idea.

...You then switch off the aerosol injection - the full solar output is allowed back in and suddenly you have the extra 50 ppm CO2 at work instantly and not a gradual increase that would allow absorption by the oceans.

This is possible, but it is just one scenario, and, honestly, not the most probable one.1. You switch off aerosol injection, why?2. "...extra 50 ppm CO2 at work instantly..." - come on, 50 ppm [@400 level] is just 12%. That is far cry from doubling concentration, which would allegedly increase global temp by 2 degrees.3. You pretend to know what heat balance between land and ocean is, but in reality, you have not a slightest idea.

Sorry, I'm done on here spelling out to peeps ad nauseum and in words of one syllable - the questions you ask are in plain sight in the above article. Read it properly.Also, I suppose you have the "slightest idea" do you? and I pretend? really. I would suggest I have a tad more "idea" than you my friend.

The IPCC predicts, in 2050 that the temperatures will increase (after a 50ppm rise to 460 ish) to be 0.8 - 2.6°C higher than today. Let's assume they're correct (despite their projections being wrong the majority of the time).

You're now telling us that we spray aerosol sulphates into the air for 30 years, ironically landing us very close to 2050, and you're telling us the same 450ppm (ish) is going to be up to 5.2°C change. How?

Oceans wont absorb the sudden heat? Oceans have had 30 years to offload heat from the cooling. If oceans can't loose heat now being 90% capacity as you say, and warming is inevitable, then surely the same rule of "the oceans cant handle it and it all goes into the atmosphere" applies sulphates or no sulphates?

Sorry runrig, that isn't RATE of warming, that is just a buffer being removed and a true value being displayed.

You're now telling us that we spray aerosol sulphates into the air for 30 years, ironically landing us very close to 2050, and you're telling us the same 450ppm (ish) is going to be up to 5.2°C change. How?

Oceans wont absorb the sudden heat? Oceans have had 30 years to offload heat from the cooling. If oceans can't loose heat now being 90% capacity as you say, and warming is inevitable, then surely the same rule of "the oceans cant handle it and it all goes into the atmosphere" applies sulphates or no sulphates?

Again, a climate scientist wanting the fact to swing both ways.

On the contrary no, sorry triple…I tried to make it words of one syllable – trying for the last timePS: I'm not saying this is the answer – just what I think it is.

It's like holding back coiled spring. But one that is increasing it's tension while held.

We keep temps to current levels artificially by the use of aerosol injection.For the period of time we do that Anthro GHG's in the atmosphere increase.

(what this article says) is IF we then STOP the aerosol injection. The warming would spring back at an enhanced rate and soon get to where it would have been had we never attempted to use aerosol albedo increase. AND due to the lack of absorption during that period by Oceans – the heat would be manifested quickly and exaggeratedly in the atmosphere, due to stronger feed-backs.Any clearer?

Oceans will take hundreds of years to lose the excess heat they've gained due to AGW. Much longer than the absorption process. FFS it takes ~1000 years for complete circulation of the Ocean currents.Heat in the oceans is effectively "locked away". And thank Christ it is – for that is what gives inertia to the system.

Rimino

(what this article says) is IF we then STOP the aerosol injection. The warming would spring back at an enhanced rate and soon get to where it would have been had we never attempted to use aerosol albedo increase. AND due to the lack of absorption during that period by Oceans – the heat would be manifested quickly and exaggeratedly in the atmosphere, due to stronger feed-backs.Any clearer?

No, it isn't, because you're exxagerating the energy coming into the system (Earth). Once again you used the word rate.

Look. The sun gives out X amount of energy, the earth absorbs Y amount of energy. Having a "screen" up reflecting some energy, and then taking it down again, isn't suddenly going to double the warming.

50ppm of CO2 isn't going to double the rate. The earths rate of warming is directly proportional to energy intake from the sun, of which CO2 is a very minor GHG compared to water vapour etc.

I'm not saying there won't be an increase. CO2 is a GHG and as CO2 builds up and being screened, it will be a "sudden" intake of extra energy as more CO2 is present to absorb that heat.

I just think it doubling from that amount of ppm is sheer lunacy.

Venus is 965,000 ppm (96.5%). If 50ppm can increase rate of temperature by double, and allow 5°C increase within decades, then if we take this CO2 rate vs temp rate and extrapolate, venus should be 965,000 / 50 = 19300 x 5°C = 96,500°C. Of course, Venus is closer to the sun, and smaller than earth, and no oceans as buffer, so it may even reach 100k°C. No, its 450°C average.

CC scientists say Earth could have a runaway GHG effect like Venus. 450ppm vs 965,000 ppm, and they're saying it's a similar situation...That's like saying the island of hong kong is almost as big as the sun. It's a retarded statement.

Yes rate of warming will increase with a sudden 50ppm difference. Double? No. Of course not.

Look. The sun gives out X amount of energy, the earth absorbs Y amount of energy. Having a "screen" up reflecting some energy, and then taking it down again, isn't suddenly going to double the warming.

50ppm of CO2 isn't going to double the rate. The earths rate of warming is directly proportional to energy intake from the sun, of which CO2 is a very minor GHG compared to water vapour etc.

It is complete nonsense to suggest a doubling of intake of energy.

Either I'm not explaining this clearly or you are being obtuse – I think the later.I say "rate" because I mean rate.

Earth's rate of warming is directly proportional to energy intake from the Sun, yes, but only as a complete system. Here they refer (IMO) to global air temps. Oceans are sequestering the heat at a rate commensurate with ocean current overturning.Please don't bring up the myth of WV vs CO2 GHG equivalency – it's irrelevant except to denialists. Sorry, the science is perfectly clear.

In a situation where you hold an effect back thereby allowing the causative agent to increase over (say) 30 years) and then remove the blocking agent. Why on earth would you expect it to carry on it's warming effect at the same rate it was interrupted at 30 yrs prior?

It is an artificial situation because the incoming excess SolarSW in the natural situation would have been sequestered at a 90:10 sea:air proportion in that case (as time and steady increase permitted it). In the artificial case you suddenly get that 30 yrs of GHG warming effect in one hit and SolarSW will heat the atmosphere differentially greater - heat entering the oceans requires a circulation to take it away and bury it in deeper waters (10's yrs -globally), whereas the atmosphere will respond quickly.On top of that the faster heating of air vs seas will mean a bigger/faster +ve feed-back of ice melt/albedo decrease.

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A review published in The Lancet Neurology journal states that the news is so troubling, they are calling for a worldwide overhaul of the regulatory process in order to protect children's brains.

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